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TITLE: Adjustment of food textural properties for elderly patients
AUTHOR: J. A. Y. Cichero 1,2,3
1 Honorary Senior Fellow, School of Pharmacy, The University of Queensland,
Australia
2 Senior Speech Pathologist, The Wesley Hospital, Brisbane, Australia
3 Co-Chair, International Dysphagia Diet Standardisation Initiative, Brisbane,
Australia
Running title: Food texture properties suitable for the elderly
Corresponding author:
Dr Julie A Y Cichero
Address for correspondence:
School of Pharmacy
Pharmacy Australia Centre of Excellence
The University of Queensland
20 Cornwall Street
Brisbane, QLD, Australia
Email for correspondence:
This article has been accepted for publication and undergone full peer review but has not beenthrough the copyediting, typesetting, pagination and proofreading process which may lead todifferences between this version and the Version of Record. Please cite this article as an‘Accepted Article’, doi: 10.1111/jtxs.12200
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Food texture properties suitable for the elderly
2
ABSTRACT:
Over the next twenty years the number of people over 60 years will exceed one billion.
Changes associated with ageing have an impact on food texture choices for healthy
elders and those used therapeutically for people with swallowing difficulties
(dysphagia). The ideal ‘swallow-safe’ bolus is moist, cohesive and slippery. A general
reduction in muscle strength is seen throughout the ageing oropharyngeal musculature,
resulting in a reduced ability to safely and efficiently manage hard or fibrous textured
foods. Reduced masticatory ability combined with dental loss further compounds the
issue. Dry mouth is commonly associated with old age, making it difficult to propel
dry or sticky textures through the pharynx, and increases the likelihood of pharyngeal
residue. An age related reduction in laryngopharyngeal sensitivity dampens the ability
to detect residue, increasing choking risk. Reduced tongue pressure, increases in
pharyngeal transit time, valleculae residue, number of clearing swallows and slower
and less efficient oesophageal transit occur with aged swallowing. Food textures that
are sticky and adhesive will require increased lingual effort to propel them into and
through the pharynx. Taken in combination these factors mean that food textures
prescribed to the elderly need to be soft and moist and for fibres to be easily broken.
To improve moisture content, additional nutrient dense products (e.g. milk, cream or
butter) may be required to artificially moisten the bolus. Careful, individualised
attention to diet recommendations will result in a diet that is appealing and also
provide a variety of textures that are swallow-safe and nutrient dense.
KEY WORDS: choking risk; food textures; elderly; dysphagia; swallowing; dry
mouth
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PRACTICAL APPLICATION:
Aged related changes in the oral cavity and the oral, pharyngeal and oesophageal
phases of swallowing require special thought to the suitability of food textures for the
elderly. Foods that are fibrous, hard or dry may be unsuitable due to difficulties with
safe particle size reduction and bolus formation for swallowing. Foods that are sticky
and adhesive are also problematic and increase risk for both choking and residue.
Food texture properties that are ideally suited for the elderly include those that are
soft, moist, and easily reduced with minimal chewing effort. Hard food textures that
break down and dissolve easily with minimal chewing should be investigated.
Increased aroma and flavour may improve appeal lost through reduced variety in food
textures. Diet reviews need to consider both textures that can be safely managed and
the nutrient density of those textures.
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1.0 INTRODUCTION
Compared to fifty years ago, the average person is living 20 years longer, and the
World health Organization notes that for the first time, most people can expect to live
into their sixties and beyond (World Health Organization, 2015). Changes associated
with ageing have an impact on food texture choices for healthy elders and food
textures used therapeutically for people with swallowing difficulties (dysphagia). For
individuals of any age, there are certain bolus properties that promote safe and
efficient swallowing (Loret et al. 2011). However, changes associated with aging
such as reduction in muscle strength, changes to dentition and salivary flow, and
alterations in sensory experiences such as aroma and taste come to effect the type of
food elderly people consume (Achem & DeVault 2005). These choices affect nutrient
density and can predispose to malnutrition (Popper & Kroll 2003; Taylor & Barr
2006; Charlton et al. 2010). This review will describe ideal food properties for safe
swallowing. It will then focus on structural and physiological changes that occur with
aging and their impact on food texture preferences and swallow safety. It will
conclude with specific examples of food texture properties suitable for the elderly.
2.0 THE ‘IDEAL’ SWALLOW-SAFE BOLUS
For individuals of any age, a bolus is chewed until it is generally of homogenous
texture. For hard textured foods, particles are generally reduced to particle sizes of
~1.4-2mm each (Peyron et al. 2004; Foster et al. 2011). For softer foods (e.g.
banana), larger particle sizes are tolerated. The over-arching requirement of oral
preparation is to reduce the food to a texture that is swallow-safe and will avoid injury
to the mucosa of the oral cavity, pharynx and oesophagus (Prinz & Lucas 1995;
Mishellany et al. 2006; Foster et al. 2011; Peyron et al. 2011). In order to achieve
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this, a moisture content of the final bolus for cereal based foods has been reported to
be around 50% (Loret et al. 2011). For other foods moisture content is achieved
through inherent moisture in the food and supplementation with saliva that is released
during chewing and oral preparation. Foods that have a high water content may need
very little saliva added, whereas very dry foods (e.g. nuts), will require significantly
more saliva and more chewing to moisten the bolus (Mishellany et al. 2006). For
differing meat textures, moisture content at the point of swallow readiness was found
to be the same, despite differences in level of fibre disorganization (Yven et al.
2006)The final swallow-safe bolus is soft, homogenous in texture, cohesive and
slippery enough to allow ease of swallow initiation and swift transport through the
pharynx (Hoebler et al. 1998; Loret et al. 2011; Motoi et al. 2013).
3.0 CHANGES TO THE INTEGRITY OF THE CHEWING AND SWALLOWING
MECHANISM ASSOCIATED WITH AGING
A general reduction in muscle strength is seen throughout the ageing oropharyngeal
musculature resulting in a reduced ability to safely and efficiently manage hard or
fibrous textured foods (Kohyama et al. 2002; Hall & Wendin 2008). Anterior and
posterior tongue strength is reduced as individuals age (Butler et al. 2011). The
tongue has a key role in manipulation and placement of the bolus between the molar
surfaces for chewing, and removal of residue from in and around tooth structures.
Following oral preparation of the bolus the tongue shapes and collects the bolus in
readiness for swallow initiation and then propels the bolus from the oral cavity to the
pharynx. There are also efficiency changes associated with reduced muscle strength in
the pharyngeal phase of swallowing. The superior, middle and inferior pharyngeal
constrictors have a role in clearing the tail of the bolus through the pharynx and into
the oesophagus. Increases in pharyngeal transit time, valleculae residue, and number
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of clearing swallows are associated with the aged swallow (Donner & Jones, 1991;
Dejaeger et al., 1997; Rademaker et al. 1998). Finally, reduced oesophageal transit
and oesophageal abnormalities such as tertiary contractions and achalasia may also be
seen, further impeding flow of the bolus from the oesophagus to the stomach (Shaker
& Lang 1994; Dejaeger et al. 1997). Certain food textures (e.g. hard, dry, fibrous)
become more challenging to manage in the context of ageing swallowing system (Lee
& Anderson 2005).
3.1 Dental loss and food texture choices
Whilst it is well known that aging causes systemic changes to skeletal muscles, the
effect on the masticatory system is more complex than those of the limb and trunk, for
example (Grunheid et al. 2009). The jaw muscles have an abundance of hybrid fibres
including both slow and fast twitch muscle fibres that contribute to precise
modulation of jaw position and force during mastication (Korfage et al. 2005).
Furthermore there are large individual variations in fibre-type composition. Like limb
and trunk muscles there is a reduction in density of cross-sectional masticatory
muscle fibres (Korfage et al. 2005), however in elderly individuals the proportion of
pure Type I fibres decreases while the number of Type II and hybrid fibres increase
(Korfage et al. 2005). Grunheid et al. (2009) reported that muscles have an inherent
ability to adapt to changing needs. For example, overloading and increased muscle
activity leads to slower, fatigue resistant fibres, whereas unloading and reduced
muscle activity leads to transition towards faster, more fatiguable fibre types.
A series of inter-connected elements may drive the changes noted above in human
jaw muscles. Firstly, tooth loss is common in the elderly and has prompted initiatives
such as the Japanese 8020 campaign for the elderly to retain 20 teeth by 80 years of
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age (Yamanaka et al. 2008). This initiative is supported by studies by Kayser (1981,
Kaiser et al. 1987) who showed that a minimum of four symmetrical occlusal units
and six asymmetrical occusal units were required for adequate masticatory function
with an over-riding recommendation for retention of 10 occlusal surfaces (12 front
teeth, 8 pre-molars). Loss of occlusal units affects bite force such that those with
greater than 20 teeth (10 paired occluscal units) have a bite force of 555 N , in
contrast to an exponential decline in bite force with a reduction in remaining teeth; for
example 383 N for 10-19 teeth remaining; 180 N for 1-9 teeth remaining and 155 N
for edentulous individuals (Yamanaka et al. 2008). Korfage et al. (2005) noted that
removal of all incisors and molars in a monkey model demonstrated a reduction in
masticatory muscle mass, a decrease in slow twitch masseter muscle fibres and an
increase in masseter fast twitch, fast fatiguable fibres.
In addition to tooth loss, the effect of food hardness may have an effect on the
composition of jaw muscle fibres. Although there are no human studies reported,
animal studies indicate that provision of a soft diet in a rabbit model results in a
reduction in Type I (slow twitch) fibres and an increase in Type II (fast twitch) fibres
(Korfage et al. 2005). This discussion highlights a clear inter-relationship between
number of occlusal units, bite force, and muscle changes adapting to reduced usage.
Consequently diet becomes both an impact on and an outcome of dental status in the
elderly. Note also, the link between dental status and choking risk. There is a high
correlation between absent teeth, ill-fitting dentures, dental disease and sudden
choking deaths (Berzlanovich et al. 2005; Wick et al. 2006). Pereira et al. (2006) and
Okamoto et al. (2012) have found that individuals with dentures have only 25% of the
chewing effectiveness of dentate people and produce a coarser bolus that has larger
particles. Fibrous foods (meat), hard food (raw fruit and vegetables), and mixed
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consistency textures become more challenging with age (e.g. soups with noodles,
meat, vegetables, chicken or fish with bones) (Lee & Anderson 2005; Hall & Wendin
2008). Softer, easy-to-chew options are more likely to be chosen.
3.2 Food texture modification for safety
Healthy elders will typically choose soft textured food by preference. Individuals
with swallowing difficulties as a result of stroke, neurological conditions, head and
neck cancer or other conditions require a range of degrees of food texture
modification (Wright et al. 2005; Germain et al. 2006). There are typically three
levels of food texture modification plus regular food. These often include foods that
are (a) soft, (b) minced and moist or mashed, and (c) pureed or ground (Cichero et al.,
2013). Most recently, the International Dysphagia Diet Standardisation Initiative
(IDDSI) released international descriptors for food texture modification for
individuals with swallowing difficulties (IDDSI 2015). The IDDSI framework is a
continuum of eight levels (0-8) addressing both food and drink texture modification
on a single continuum (IDDSI 2015). For foods, as with all published national
terminologies, each category of food texture modification requires the bolus to be soft
and moist (Cichero et al., 2013; IDDSI 2015). Degrees of modification then largely
reflect homogeneity of particles and particle size. Soft food textures can be mashed
with a fork but may have disparate particle sizes, whilst pureed or ground food has
very small particles that are homogenous in texture and size. The recommendations
regarding food texture features, including size and shape are informed by autopsy
results and non-fatal choking incidents (Rimmel et al. 1995; Berzlanovich et al. 1999;
Centre for Disease Control and Prevention 2002; Morely et al 2004; Food Safety
Commission Japan 2010; Chapin et al. 2013; Siddell et al. 2013; Kennedy et al. 2014).
Whilst more people choke in the community or at home, choking still occurs in
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hospital settings (69% and 9.5-27% respectively) (Berzlanovich et al. 2005). The
types of food individuals choke on includes sausages, sandwiches, meat, vegetables,
noodles, and the less intuitive puree, ground meat and mashed fruit (Cichero 2015).
In addition to food textures or shapes that increase choking risk, person-features must
also be considered. Individuals with cognitive impairment, oral phase impairment
and those with an intellectual disability are at higher risk of choking (Samuels et al.
2007). Individuals with missing or compromised teeth are at increased risk of
choking (Berzlanovich et al. 1999, 2005; Wick et al. 2006); and individuals with
reduced bite force and chewing ability are likewise at increased risk of choking (Chen,
2009).
3.3 Hard food, fibrous food and ‘dissolvable’ hard food textures
For individuals who experience fatigue during chewing, but have otherwise good
control of the bolus, it may be sufficient to cut hard textured food to smaller ‘bite-
sized pieces’ to reduce the masticatory load. Indeed a recommendation from a
systematic review of choking deaths considers small particle size recommended
management to reduce choking risk (Kennedy et al. 2014). The human thumbnail
measuring about 1.5cm, provides a reasonable reference point for a particle size that
is large enough to chew, yet small enough to require fewer chewing actions (Murdan
2011). Indeed this size is often used in sensory testing, and has been reported in
published national terminologies (National Dysphagia Diet Task Force 2002;
Kohyama et al. 2002; Mishellany et al. 2006; Atherton et al. 2007; National Patient
Safety Agency UK 2011; Duan et al. 2014).
Fibrous foods are complex food textures for oral preparation and are often identified
on autopsy studies as choking risks (Berzlanovich et al. 1999, 2005; Wick et al. 2006;
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Food Safety Commission Japan 2010). Safe chewing and swallowing of fibrous foods
requires an ability to break the fibrous framework and then reduce the particles to a
size and form that is swallow safe. Rotary chewing using the molar teeth and
sufficient stamina is required for this process. For meat products, cutting across the
grain makes fibres shorter and therefore easier to chew (Purslow 2005).
Anecdotally and from clinical experience, individuals who require soft, minced or
pureed food textures often miss the ‘crunch’ and textural variety offered with hard
textured foods. There is a class of hard food textures referred to clinically as
‘dissolvable’ or ‘melt-in-the-mouth’ textures that have a regular hard texture
appearance, but with the addition of moisture and little chewing are easily broken
down to a swallow-safe bolus (Gisel 1991; Dovey et al. 2013). These foods have been
used clinically most often with the paediatric or disability populations to teach
chewing skills (Dovey et al. 2013). However, they could be used effectively for the
elderly who wish to experience the sensory qualities that hard textured food provides
with the benefit that little chewing strength or stamina and minimal saliva is needed
for oral preparation. Some examples include potato crisps, wafers, and prawn crackers
or crisps (Gisel 1991; Dovey et al. 2013; Duan et al. 2014). ‘Dissolvable’ foods have
also been described in the International Dysphagia Diet Standardisation Initiative
framework in the ‘transitional foods’ section (IDDSI 2015).
3.4 Sticky and adhesive foods
As noted above, there is a reduction in tongue strength associated with aging (Butler
et al. 2011). Sticky and adhesive foods such as nut butters, sticky rice and festive
sticky rice cakes have been associated with increased choking risk (Wick et al. 2006;
Food Safety Commission Japan 2010). The tongue force required to initiate
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movement of this type of food texture, resistance offered to movement and potential
to stick to structures such as the hard palate or gingiva with unexpected or
uncontrolled release once sufficiently softened with saliva increases choking risk.
Sticky and adhesive food textures should be avoided in frail elders and individuals
with swallowing difficulties (Berzlanovich et al. 2005; Kennedy et al. 2014).
3.5 Boost aroma and flavor to compensate
Where food texture modification is essential for safe swallowing and to reduce
choking risk, alternatives to texture are required to increase the appeal of the food.
Chewing releases flavor volatiles as particle mix with saliva throughout the oral phase,
whereas foods that require little or no chewing results in retronasal flavor appreciation
that occurs after the swallow (Foster et al. 2011). Boosting flavor and aroma provides
one way to increase the sensory experience, although both of these sensory areas are
somewhat degraded with aging (Popper & Kroll 2003). There are studies, however,
that have shown that the ability to appreciate particular food flavours are preserved
and have been shown to provide a statistically significant increasing in food appeal.
For example the inclusion of oyster sauce, ginger, and garlic along with judicious use
of foods that excite the intact trigeminal system (e.g. heat of chili, pungency of
mustard) have been shown to increase food intake in the elderly (Henry et al. 2003;
Delahunty et al. 2004).
4.0 INTEGRITY OF THE BOLUS PATHWAY
The discussion above has focused on the integrity of the chewing mechanism and
food textures properties that help to create a swallow-safe bolus. However, attention
must also be paid to integrity of the bolus pathway. Even a slippery, cohesive bolus
will travel more slowly and require greater effort to propel if the bolus pathway (i.e.
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oral, pharyngeal and/or oesophageal mucosa) is dry. Healthy saliva production is
essential to the slippery texture of the final bolus in addition to the integrity of the
oropharynegal and oesophageal mucosa. Both watery and viscous saliva are produced
(Humphrey & Williamson 2001). Mucins within saliva help to provide the ‘slippery’
quality that lubricates and assists with bolus transport (Bongaerts et al. 2007). Saliva
has a role in dissolving tastants during chewing which enhances flavor perception,
and also offers a role in temperature regulation of the bolus. Saliva includes enzymes
that help initiate carbohydrate digestion (e.g. amylase and lipase), whilst also
providing an acid-base balance to manage reflux and bacteriostatic and bactericidal
function to protect the oral cavity (Humphrey & Williamson 2001). Thus saliva has a
key role in keeping the oropharynx and oesophagus moist and in good condition. A
slippery bolus will travel far more effectively along a pathway that is also moist and
lubricated, reducing the likelihood of residue or the need for multiple clearing
swallows.
Liedberg & Owall (1991) investigated the effect of saliva loss on chewing and
capacity for oral food perception. Healthy individuals received intramuscular
injections of 0.5 mL of methylscopolamine nitrate to temporarily restrict saliva flow
during the chewing experiments. The authors noted when compared to normal saliva
function, that a chemically induced reduction in saliva resulted in a lack of perception
of food particles in the oral cavity, difficulty collecting and forming a bolus and
difficultly initiating the swallow reflex. Hydrophilic foods that particulate (e.g. nuts,
crackers, cookies) pose a particular problem in this regard, compromising swallowing
safety. A reduction in saliva occurs as a natural part of the ageing process and is
exacerbated by medication side effects that cause dry mouth. (Cassolato & Turnbull
2003). Xerostomia, or dry mouth, thus affects the ability to form a swallow-safe bolus
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with sufficient moisture content and also increases the dryness of the bolus pathway,
thereby increasing risk for residue and need of multiple swallows to clear the bolus
(Lee & Anderson 2005). Both of these features increase choking risk. Hard, dry,
sticky and adhesive foods require large amounts of saliva, also making these textures
unsuitable for individuals with dry mouth conditions. Further compounding these
effects, there is an age related reduction in laryngopharyngeal sensitivity that
dampens the ability to detect residue (Martin et al. 1994). Residue may be inhaled
after the swallow, increasing choking risk.
5.0 FOOD TEXTURE MODIFICATION AFFECTS NUTRIENT DENSITY
Although elderly people are less active than younger people, their need for most
nutrients does not change (WHO 2015). Consequently malnutrition is a concern for
the elderly (WHO 2015). The need to avoid entire classes of food texture such as hard,
dry, fibrous, sticky and adhesive foods impacts on whole food groups necessary for
adequate nutrition. For example, the need to avoid these types of textures affects the
ability to consume iron-rich protein (meat, poultry, fish, nuts, seeds etc.), foods
containing vitamins and minerals (raw fruits and vegetables) and foods containing
dietary fibre (fruits and vegetables). Texture modification such as puree requires the
addition of liquid to ensure the final product is moist. Nutrient dilution can occur if
food is pureed with water. Nutrient-rich alternatives such as milk, butter, cream,
cheese, gravy, creamy soup or sour cream could be used to add moisture to pureed
food instead. Some individuals may safely manage a small amount of regular
textured food but benefit from nutrient-rich, high calorie supplements to meet their
nutritional needs.
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The consequences of inadequate nutrition are sobering. Malnutrition results in
reduced muscle mass that often results in reduced functional ability, thereby
increasing dependence on others. Increased risk of infection and poor wound healing
(e.g. pressure sores) are also associated with malnutrition (Litchford et al. 2014).
Eating smaller amounts also results in gut atrophy. Attention is needed to both
nutritional content and swallow-safe food textures that can deliver these needs to
elderly people.
6.0 CONCLUSION
Food textures prescribed to the elderly need to be soft or for fibres to be easily broken.
The bolus needs to be moist and lubricated to overcome issues associated with
passage of the bolus over dry oropharyngeal mucosa. This may mean that additional
nutrient dense moisture (e.g. milk, cream or butter) is required to artificially moisten
the bolus. Hard, dry foods should generally be avoided, with the exception of
‘dissolvable’ solids. Careful, individualised attention to food textures will result in a
diet that provides a variety of textures, that is swallow-safe and able to meet the
person’s nutritional needs.
CONFLICT OF INTEREST: The author declares that she does not have any conflict
of interest.
ETHICAL REVIEW: This review does not involve human or animal testing.
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